1. Field of the Invention
The present invention relates to an overhead traveling vehicle system, and in particular relates to a system in which an overhead traveling vehicle track and a local carriage track are arranged in a vertically overlapping manner over a load port.
2. Description of the Related Art
The inventor of the present invention has proposed arranging an overhead traveling vehicle track, a local carriage track, and buffers in a vertically overlapping manner over a load port (see, for example, JP 2012-111635A). This makes it possible to stock buffers with articles that are to be carried to and from the load port. In JP 2012-111635A, the buffers are arranged directly under the local carriage track, on both the upstream side and the downstream side of the load port, and the buffers are connected by a frame that is parallel to the track. This frame is provided with an obstacle sensor that monitors the area on the passageway side of the load port so as to prevent hoists or the like from coming into contact with an operator attempting to access the load port, for example.
However, with this arrangement, if a hoist or an article horizontally swings, there is the possibility of coming into contact with the frame over the load port. Also, although overhead traveling vehicles are generally provided with a sensor that detects an obstacle in the vicinity of the load port, there is the possibility of the local carriage track or the buffer frame being mistakenly detected as an obstacle by the sensor.